Radiation directing structure



Nov. 30, 1965 w. s. MILLER RADIATION DIRECTING STRUCTURE Filed. Aug. 15, 1962 INVENTOR.

. M/LLZE A'r'roczNsv WENDELL 5 United States Patent 3,221,163 RADIATION DIRECTING STRUCTURE Wendell S. Miller, 1341 Comstock Ave., Los Angeles, Calif. Filed Aug. 15, 1962, Ser. No. 217,092

2 Claims. '(Cl. 240-41.3)

This invention relates to an improved type of radiation directing structure, such as a Searchlight, carbon arc furnace, microwave antenna system, or other electromagnetic radiation emitting unit. The invention will be discussed primarily as applied to searchlights, though it will be apparent that certain features of the invention are equally applicable to the above mentioned other uses.

A radiation directing structure embodying the invention includes a source of radiation, such as a carbon arc, and a ray concentrating element for reflecting or retracting the light rays or other radiation in a manner producing a beam which is aimed in a predetermined direction, and is centered essentially about a particular axis. The concentrating element is generally a conventional reflector or mirror, but may in some cases be a lens. The concentrating element occupies a portion but not all of a half space which is defined by a plane disposed perpendicularly to the specified axis and extending generally through the radiation source.

In designing a Searchlight or other radiation directing arrangement, it is usually impossible to provide a concentrating mirror or lens which can extend through an entire half space, as viewed from the radiation source, and which can elfectively reflect rays from the source throughout the entire angular extent of that half space, in a manner bringing all of the emanated rays into proper alignment in the ultimate projected beam. Consequently, in conventional Searchlight structures and the like, the radiation within a portion of the half space which contains the concentrating element is almost invariably wasted, and does not form a part of the emitted beam. The general object of the present invention is to conserve the energy which is thus lost in ordinary search-light arrangements and the like, and utilize that energy in a manner acting to increase the efliciency of the radiation, lengthen the active life of the radiation source, and/or increase the brightness of the projected beam. This result is attained by providing unique supplemental reflectors which are positioned to receive the radiation emitted by the source into the portions of the defined half space which are not occupied by the primary concentrator element, and which function to reflect this energy which would otherwise be wasted back toward the source to assist in maintaining or increasing its temperature. Where the primary concentrator is an annular mirror of parabolic or other shape, two supplemental reflectors may be employed, positioned to occupy two portions of the half space which contains the main reflector, with those two portions being located angularly within and angularly outwardly beyond the main reflector, as viewed from the radiation source. The supplemental reflector or reflectors preferably take the form of ellipsoids of revolution, and for maximum ease of manufacture may be shaped as spheres centered about the radiation source, a sphere being a special case of an ellipsoid of revolution.

The above and other features and objects of the inven tion will be better understood from the following detailed description of the typical embodiments illustrated in the accompanying drawing, in which:

FIG. 1 is an axial section through a first form of searchlight constructed in accordance with the invention; and

FIG. 2 is a similar view showing a second form of the invention.

The searchlight shown in FIG. 1 includes a cylindri- 3,221 ,163 Patented Nov. 30, 1965 cal housing 11 centered about an axis 12, and mounted on a suitable support or base structure 13. The front side of the housing (the left side as seen in the figure) is open to the discharge of the beam of light therethrough. To protect the inner parts within the housing, however, this side may have a transparent circular glass 14 mounted therein, and connected to the periphery of the cylindrical side wall 15 of housing 11 by a mounting ring 16. For the purposes of discussion of the first form of the invention, it may be assumed that glass 14 has little or no eflect as a lens, and does not substantially retract or change the direction of the light rays emanating from the interior of the housing.

The source of light within housing 11 of FIG. 1 is an essentially conventional carbon arc structure 16, including the usual carbon and iron electrodes 17 and 18 respectively. These electrodes may typically be centered about axis 12 of the housing, with iron electrode 18 being rigidly mounted to the rear wall 19 of the housing by a mount structure 20, and with the carbon electrode 17 being mounted by the usual adjusting apparatus for movement axially toward and away from electrodelS. The carbon electrode 17 may be supported by a spider 21 extending outwardly for connection to side wall 15, and relative to which electrode 17 is adjustable rearwardly and forwardly toward and away from electrode 18 by turning an adjusting handle typically represented at 22. Electrical energy is supplied to the electrodes by leads il lustrated diagrammatically at 23 and 24.

The light produced by formation of an electric are between electrodes 17 and 18 emanates primarily from a small pool or projection of high temperature carbon 25 located at the center of the rearwardly facing surface of the carbon electrode. A large portion of the light emitted from this point 25 is received by the main reflector 26 of the Searchlight, and is reflected leftwardly by that reflector to form a beam emitting from the apparatus in the general direction of the arrows 27. This beam may be a flaring beam, a converging beam, or a beam of parallel rays, depending upon the particular construction of reflector 26. Where it is desired to produce a beam having rays as parallel as possible, as is usually desired, mirror 26 is a paraboloid of revolution formed by revolving about axis 12 a parabola whose focus is located at the point 25. Similarly, diverging rays may be produced by forming reflector 26 as a hyperboloid of revolution, and converging rays may be produced by forming reflector 26 as an ellipsoid of revolution having one of its foci at point 25. In any of these three cases, the mirror 26 is a conoid of revolution.

Mirror 26 is annular, extending from an inner circular edge 28 to an outer circular edge 29 at which the reflector may be secured in suitable manner to side wall 15 of the housing. Thus, the mirror 26 receives and properly directs light rays coming from the source 25 through an angular extent or region represented at a in FIG. 1. It is noted, however, that this angular extent a of reflector 26 consists of only a portion of the angular extent of the full half space viewed from source 25 when looking rearwardly, that is, the half space to the rear of a plane 30 disposed transversely of axis 12 and extending through light source 25. Inwardly of mirror 26, there is a region b of the specified half space within which radiation from source 25 can not impinge upon mirror 26, and similarly, there is an angular region or distance 0 which is outwardly of mirror 26, as viewed from source 25, and within which rays can not impinge upon reflector 26.

To conserve the energy radiated from source 25 within the angular regions designated b and c, I provide in these areas two circular supplemental reflectors 31 and 32, which act to reflect energy received from source 25 back toward the source. Reflectors 31 and 32 have inner specularly reflective concave surfaces facing toward and centered essentially about point 25 to attain the desired purpose. Mirror 31 may be received about and mounted to electrode 13, and extend outwardly to a peripheral circular edge 33 which is at the periphery of the angular region b. The second supplemental mirror 32 is annular, and may be mounted in the illustrated position in any suitable manner, as by connection to spider 21 by a pair of arms or other mounting brackets 34 which meet and are connected to mirror 32 at plane 30.

It is noted that both of the supplemental mirrors 31 and 32 are located inwardly far enough to avoid substantial obstruction of the beam being projected leftwardly by main reflector 26. For this purpose, neither of the supplemental reflectors 31 or 32 should be located in axial alignment with any portion of mirror 26, and desirably both supplemental mirrors 31 and 32 have a maximum diameter which is not greater than the minimum diameter of inner edge 28 of mirror 26.

With more specific regard to the shapes of mirrors 31 and 32, these mirrors should be ellipsoids of revolution, formed by revolving about axis 12 ellipses whose foci are both located at approximately the position of light source 25. It will be apparent that this light source may have substantial extent transversely of axis 12, and therefore the foci of the specified ellipses may be offset somewhat from axis 12, preferably at diammetrically opposite sides of the light source. For simplicity of manufacture, satisfactory results may in most cases be attained by forming the reflectors 32 and 33 as spherically curved surfaces, centered about the exact center of light source 25, which is of course located on axis 12.

In using the Searchlight of FIG. 1, the operator supplies current to leads 23 and 24, to develop an arc of appropriate length between the electrodes 17 and 18. The light and heat energy produced at point 25 then radiates outwardly throughout the entire half space to the right of plane 30, and the portion of that radiation which falls within the angular region a is reflected by a reflector 26 to form a beam projected outwardly to the left from the device. The energy radiated within angles 12 and c, on the other hand, can not strike and be utilized by mirror 26, but instead strikes mirrors 31 and 32, and is reflected through an essentially 180 degrees reflection by these mirrors directly back to source 25. This reflected radiation supplements the heating of the electrode at 25 by the arc, and therefore tends to increase the brightness of the beam produced by the searchlight, reduce the amount of scurrent drawn by the light, and in general increase the operating efliciency of the searehlight as a whole.

FIG. 2 represents another form of the invention which attains some but not all of the advantages of the FIG. 1 arrangement. Specifically the FIG. 2 searchl-ight at a utilizes a lens 26a, instead of reflector 26 of FIG. 1, for concentrating or directing the light rays to the left along lines such as those represented by arrows 27a. In FIG. 2, the carbon electrodes of the carbon arc is represented at 17a, and coacts with an iron electrode 18a to produce an arc, with the resulting light being considered as emanating primarily from point a at the front side of the carbon electrode. Iron electrode 18a may be rig-idly mounted in the illustrated position by a spider 21a, while the carbon electrode may be actuatable axially along axis 12, and toward and away from electrode 18a, by an adjusting knob 22a.

The light from source 25a which actually reaches and is refracted by lens 26a falls within an angular range designated by the letter d in FIG. 2. This angle (I does not occupy the entire half space viewed from point 25a when looking forwardly in the direction of light projection from that point, that is, the half space which is forwardly of a plane 30a which extends transversely of axis 12 and through light source 25a. To conserve the energy of the radiation emitted from point 25a within the rest of that half space, I provide an annular supplemental reflector 32a, which is essentially centered about point 25a, and acts to reflect radiation emanating from source 25a within angle e directly back to the source. Mirror 32a has the same structural characteristics as have been discussed in connection with mirror 32 of FIG. 1. The mirror 32a may be rigidly mounted in the illustrated position in any suitable manner, as by connection to the housing through brackets 34a.

I claim:

1. A radiation directing structure defining an axis, such structure comprising a solid electrode, material in a condensed state on one end of said electrode and on said axis adapted to be electrically excited to emit radiation from its surface, said material defining a plane therethrough perpendicular to said axis, a first reflective structure comprising conicoidal mirror co-axial with said axis and having a focus at said material, said mirror lying in a direction from said plane into which said material may emit radiation, a second reflecting structure comprising a mirror in the form of a portion of a sphere extending outwardly from said plane in the same direction as lies said conicoidal mirror, said spherical mirror being centered on said focus of said conicoidal mirror and being provided with an axial opening through which said conicoidal mirror may be seen from said material.

2. A radiation directing structure defining an axis, said structure comprising a solid electrode, material in a condensed state on one end of said electrode and on said axis adapted to be electrically excited to emit radiation from its surface, said material defining a plane therethrough perpendicular to said axis, a first reflective structure comprising a conicoidal mirror co-axial with said axis and having a focus at said material, said mirror lying in a direction from said plane into which said material may emit radiation, a second reflecting structure comprising a mirror in the form of a portion of an oblate spheroid the foci of Whose defining ellipses are located at said material, said portion extending outwardly from said plane in the same direction as lies said conicoidal mirror, said oblate spheroidal mirror being centered on said focus of said conicoidal mirror and being provided with an axial opening through which said conicoidal mirror may be seen from said material.

References Cited by the Examiner UNITED STATES PATENTS 445,379 1/1899 Peral 2404l.3 1,883,360 10/1932 Fortney 240-41.3 2,026,478 12/ 1935 Lisintzki.

NORTON ANSHER, Primary Examiner. 

1. A RADIATION DIRECTING STRUCTURE DEFINING AN AXIS, SUCH STRUCTURE COMPRISING A SOLID ELECTRODE, MATERIAL IN A CONDENSED STATE ON ONE END OF SAID ELECTRODE AND ON SAID AXIS ADAPTED TO BE ELECTRICALLY EXCITED TO EMIT RADIATION FROM ITS SURFACE, SAID MATERIAL DEFINING A PLANE THERETHROUGH PERPENDICULAR TO SAID AXIS, A FIRST REFLECTIVE STRUCTURE COMPRISING CONICOIDAL MIRROR CO-AXIAL WITH SAID AXIS AND HAVING A FOCUS AT SAID MATERIAL, SAID MIRROR LYING IN A DIRECTION FROM SAID PLANE INTO WHICH SAID MATERIAL MAY EMIT RADIATION, A SECOND REFLECTING STRUCTURE COMPRISING A MIRROR IN THE FORM OF A PORTION OF A SPHERE EXTENDING OUTWARDLY FROM SAID PLANE IN THE SAME DIRECTION AS LIES SAID CONICOIDAL MIRROR, SAID SPHERICAL MIRROR BEING CENTERED ON SAID FOCUS OF SAID CONICOIDAL MIRROR AND BEING PROVIDED WITH AN AXIAL OPENING THROUGH WHICH SAID CONICOIDAL MIRROR MAY BE SEEN FROM SAID MATERIAL. 